The invention described in Japanese Patent Laying-Open No. 2010-233411 (PTD 1) aims to provide a power conversion apparatus configured by cascade-connecting unit converters, and interconnected to an electric power system via a transformer, the power conversion apparatus requiring no reactors, and can have a reduced volume and weight.
Specifically, the power conversion apparatus described in Japanese Patent Laying-Open No. 2010-233411 (PTD 1) is interconnected to a three-phase electric power system via a transformer, and supplies and receives effective or reactive power to and from the three-phase electric power system. In the power conversion apparatus, the secondary windings of the transformer are formed as open windings having six terminals. A first converter group formed of a circuit in which three converter arms are star-connected is connected to three terminals of the secondary windings, and a second converter group formed of a circuit in which other three converter arms are star connected is connected to three terminals of the secondary windings. The neutral point (star-connected point) of the first converter group and the neutral point (star-connected point) of the second converter group serve as output terminals of the power conversion apparatus.